Autoantibodies specific for different isoforms of CD45 in systemic lupus erythematosus.

Nearly one-third of IgM antilymphocyte autoantibody-positive sera from patients with systemic lupus erythematosus (SLE) contain IgM antibodies to one or more 180-220-kD molecules (p180, p190, p205, and p220) in blots of glycoproteins purified from T cells by wheat germ agglutinin affinity chromatography. Identity of these IgM targets with multiple isoforms of CD45 was established by their specific depletion from T cell glycoproteins by immunoprecipitation with T191, a monoclonal antibody (mAb) that reacts with an epitope common to all CD45 isoforms. Although the anti-CD45 autoantibodies recognize higher molecular weight isoforms primarily, antigenic specificity in this system is quite heterogeneous and includes multiple distinct CD45 isoforms on different types of T cells that are, at least in part, different from those reactive with mAbs 2H4 and UCHL-1. Because CD45 is a major membrane protein tyrosine phosphatase that plays a critical role in antigen-induced T cell activation, the present data may be relevant to some of the antilymphocyte antibody-mediated immunologic abnormalities that characterize SLE and related autoimmune diseases.

Comparison of pneumococcal conjugate polysaccharide and free polysaccharide vaccines in elderly adults: conjugate vaccine elicits improved antibacterial immune responses and immunological memory.

BACKGROUND: High functional antibody responses, establishment of immunologic memory, and unambiguous efficacy in infants suggest that an initial dose of conjugated pneumococcal polysaccharide (PnC) vaccine may be of value in a comprehensive adult immunization strategy. METHODS: We compared the immunogenicity and safety of 7-valent PnC vaccine (7vPnC) with that of 23-valent pneumococcal polysaccharide vaccine (PPV) in adults >/=70 years of age who had not been previously vaccinated with a pneumococcal vaccine. One year later, 7vPnC recipients received a booster dose of either 7vPnC (the 7vPnC/7vPnC group) or PPV (the 7vPnC/PPV group), and PPV recipients received a booster dose of 7vPnC (the PPV/7vPnC group). Immune responses were compared for each of the 7 serotypes common to both vaccines. RESULTS: Antipolysaccharide enzyme-linked immunosorbent assay antibody concentrations and opsonophagocytic assay titers to the initial dose of 7vPnC were significantly greater than those to the initial dose of PPV for 6 and 5 of 7 serotypes, respectively (P < .01 and P < .05, respectively). 7vPnC/7vPnC induced antibody responses that were similar to those after the first 7vPnC inoculation, and 7vPnC/PPV induced antibody responses that were similar to or greater than antibody responses after administration of PPV alone; PPV/7vPnC induced significantly lower antibacterial responses, compared with those induced by 7vPnC alone, for all serotypes (P < .05). CONCLUSION: In adults, an initial dose of 7vPnC is likely to elicit higher and potentially more effective levels of antipneumococcal antibodies than is PPV. In contrast with PPV, for which the induction of hyporesponsiveness was observed when used as a priming dose, 7vPnC elicits an immunological state that permits subsequent administration of 7vPnC or PPV to maintain functional antipolysaccharide antibody levels.

Monoclonal antibodies against human pancreatic adenocarcinoma: distribution of DU-PAN-2 antigen on glandular epithelia and adenocarcinomas.

This report describes the distribution of antigen DU-PAN-2, defined by a monoclonal antibody raised against human pancreatic carcinoma cells, on a variety of tumors and nonneoplastic tissues. With the use of an immunoperoxidase technique, the antigen was detected on 16 of 16 pancreatic carcinomas, on 5 of 5 gallbladder or bile duct carcinomas, on the great majority of stomach adenocarcinomas, and, less commonly, on adenocarcinomas of other primary sites. Substantial intratumor heterogeneity of antigen expression was noted. DU-PAN-2 antigen was present on many types of normal glandular epithelial cells but often was more weakly expressed than on the corresponding tumors. The immunomorphology of staining, coupled with biochemical information known about the antigen, supports the notion that the DU-PAN-2 antigen is a mucin-like substance. Its relative restriction of expression on different types of glandular epithelium suggests that DU-PAN-2 antibody might be a useful reagent for helping to determine the site of origin of adenocarcinomas.

Characterization of the shed form of the human tumor-associated glycoprotein (TAG-72) from serous effusions of patients with different types of carcinomas.

Monoclonal antibody (MAb) B72.3 binds a high molecular weight tumor-associated glycoprotein designated TAG-72. This study reports the isolation and characterization of secreted TAG-72 directly from effusions of ovarian, colorectal, pancreatic, and endometrial carcinoma patients and compares them to TAG-72 derived from the LS-174T colon carcinoma xenograft. The B72.3-reactive antigen, TAG-72, was used as immunogen to produce second generation anti-TAG-72 MAbs. One of these second generation MAbs, CC49, had a higher affinity than that of B72.3 and was utilized as an affinity reagent in a procedure to purify the TAG-72 present in the serous effusions of carcinoma patients. A three-step purification procedure, utilizing heat extraction, CC49 antibody affinity chromatography, and gel filtration chromatography, resulted in 1000- to 4400-fold purifications of the TAG-72 derived from effusions, as analyzed using a double-determinant radioimmunoassay. Radiolabeled TAG-72 from each of the effusions demonstrated similar high molecular weight bands on sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Similar results from the various effusions were also obtained in Western blotting analyses. Analyses of TAG-72 from the different effusions in radioimmunoassay using five different anti-TAG-72 MAbs revealed similar binding patterns. The results of these studies thus indicate that TAG-72 obtained directly from patients with ovarian, colorectal, endometrial, and pancreatic carcinomas and the LS-174T xenograft are highly similar in terms of immunochemical properties and antigenic profile.

Antigens associated with human squamous cell lung carcinoma defined by murine monoclonal antibodies.

A panel of 12 monoclonal antibodies that preferentially react with human squamous lung carcinoma cells has been produced. All are reactive with fresh frozen sections of squamous cell lung carcinoma tissues in immunoperoxidase assays and are unreactive with lymphoblastoid cells, red blood cells, and fibroblasts in enzyme-linked immunosorbent assay. At least eight of these antibodies interact with cell surface components. These reagents can be subdivided into four groups based upon their reactivities. Groups 1 to 3 are unreactive with normal liver, lung, kidney, colon, spleen, and pancreas in immunoperoxidase assays. Group 1 antibodies (PF1/A, PF1/B, PF1/C, PF1/D, and PF1/E) are all of IgG3 subclass and immunoprecipitate nonsulfated glycoprotein components with molecular weights of 80,000 and 180,000 and a nonglycosylated polypeptide with a molecular weight of 38,000. Group 1 antibodies are also reactive with some lung adenocarcinomas and, with the exception of PF1/E, stain certain differentiated strata within normal adult plantar and fetal epidermis. Group 2 antibodies (PF2/A and PF2/B) react also with breast, gastric, and colonic adenocarcinomas and some tumors of neuroectodermal origin. Group 2 antibodies, which are both of IgG3 subclass immunoprecipitate a nonglycosylated Mr 24,000 polypeptide. Group 3 antibodies (PF3/A, an IgG1; PF3/B, an IgGM; and PF3/C, an IgG2a) react additionally with certain other tumors, as well as with normal adult and fetal epidermis. Group 4 antibodies (PF4/A, an IgG2a; and PF4/B, an IgG1) are less specific than those of the preceding groups, as they react with some normal tissues, including pancreatic islets and pneumocytes, as well as with a variety of adenocarcinomas and tumors of neuroectodermal origin. PF4/A and PF4/B immunoprecipitate Mr 100,000 and 95,000 glycoproteins, respectively.

Isolation and properties of a human pancreatic adenocarcinoma-associated antigen, DU-PAN-2.

This work describes the molecular properties of a human pancreatic adenocarcinoma-associated mucin-like antigen defined by a murine monoclonal antibody (DU-PAN-2). DU-PAN-2 antigen is a large molecule, readily detected in the body fluids of patients with pancreatic adenocarcinoma and sensitive to neuraminidase treatment and alkaline reduction. The antigen binding activity of the DU-PAN-2 immunoglobulin M antibody is markedly reduced when coupled to an insoluble matrix. Therefore, the antigen was partially purified from the serum and ascites of patients with pancreatic adenocarcinoma by ammonium sulfate fractionation and Affi-Gel-Blue chromatography to remove most of the serum proteins. Noncovalently associated proteins were further separated on CsCl/CsBr density gradients and noncovalently associated lipids removed by organic solvent extraction. DU-PAN-2 antigen was monitored by a solid-phase competition radioimmunoassay. We have been able to detect antigen reactivity and analyze its electrophoretic pattern following transfer from 1% agarose gel onto nitrocellulose paper and immunoblotting with DU-PAN-2 antibody. Antigen was also labeled metabolically with various radioactive monosaccharides and sulfates. Radioimmunoprecipitation of labeled antigen with DU-PAN-2 antibody showed two distinct broad antigen bands consistent with the immunoblotting signals. The heavily glycosylated and polydisperse nature of this antigen and the results of various enzyme treatments suggest that the DU-PAN-2 epitope is expressed on a mucin-like molecule.

Biosynthesis and glycosylation of the carcinoma-associated antigen recognized by monoclonal antibody KS1/4.

Monoclonal antibody KS1/4 recognizes an epitope expressed on the cell surface of human adenocarcinoma cells and certain epithelia. Western blotting analyses of tumor cell extracts utilizing KS1/4 reveal staining of a major Mr 40,000 band and a minor Mr 42,000 band. Both components are also detectable in KS1/4 immunoprecipitates of L-[35S]methionine- and D-[3H]glucosamine-labeled human lung tumor cell extracts. When synthesis occurs in the presence of tunicamycin or when the immunoprecipitates are treated with peptide:N-glycosidase F, a single polypeptide component (Mr 37,000) is precipitated. Immediately following translation, digestion of Mr 40,000 and Mr 42,000 glycoproteins with endo-beta-N- acetylglucosaminidase H also yields a single polypeptide component at Mr 37,000. However, over a 3-h period beginning at 10 min posttranslation, a Mr 39,000 major component and a Mr 41,000 minor component gradually appear in the endo-beta-N-acetylglucosaminidase H digests as the Mr 37,000 component gradually disappears. Analysis of tryptic glycopeptides derived from the Mr 40,000 and 42,000 components suggests that the two components differ by the addition of one extra oligosaccharide to the Mr 42,000 component. Nonequilibrium pH gradient electrophoresis/sodium dodecyl sulfate-polyacrylamide gel electrophoresis analysis of KS1/4 immunoprecipitates resolves each of the two components into multiple spots. Digestion of the KS1/4 immunoprecipitates with neuraminidase prior to two-dimensional analysis or immunoprecipitation of short pulse-labeled extracts reduces the number of spots to three each at the Mr 40,000 and Mr 42,000 positions. Digestion of the KS1/4 immunoprecipitates with peptide:N-glycosidase F, immunoprecipitation of extracts labeled in the presence of tunicamycin, or endo-beta-N-acetylglucosaminidase H digestion of immunoprecipitates of short pulse-labeled extracts prior to two-dimensional analysis results in a single series of Mr 37,000 spots, suggesting that the polypeptide portions of the Mr 40,000 and Mr 42,000 components may be identical. Endo-beta-N-acetylglucosaminidase H digestion of KS1/4 immunoprecipitates of short pulse-labeled extracts, followed by nonequilibrium pH gradient electrophoresis, V8 protease digestion, and polyacrylamide gel electrophoresis revealed an apparently identical set of polypeptides derived from each of the three Mr 37,000 spots, suggesting that the three spots derive from highly similar polypeptides.

Characterization of the colorectal carcinoma-associated antigen defined by monoclonal antibody D612.

Monoclonal antibody (MAb) D612 recognizes an antigen expressed on the cell surface of normal and malignant gastrointestinal epithelium. It is a murine IgG2a/kappa which has been previously shown to mediate killing of human colon carcinoma cells using human effector cells (which could be enhanced in the presence of interleukin-2). Sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) analyses of MAb D612 immunoprecipitates of extracts of L-[35S]methionine-, L-[3H]leucine-, and D-[3H]glucosamine-labeled human colon carcinoma cells showed that the D612 antigen is a Mr 48,000 glycoprotein. Similar estimates of molecular mass were obtained from SDS-PAGE analyses of MAb D612 immuno-precipitates of radioiodinated extracts of surgically resected colon carcinoma and adjacent normal colonic mucosa. D612 antigen was not detectable in immunoprecipitates of supernatant media from radiolabeled cell cultures, suggesting that the antigen is not readily shed from the surface of cultured cells. The D612 antigen was shown to be clearly distinct from previously described gastrointestinal carcinoma-associated glycoproteins: the D612 antigen shows a migration pattern of SDS-PAGE distinct from those of the antigens recognized by MAbs KS1/4 and GA733, and reciprocal immunodepletion analyses of D-[3H]glucosamine-labeled colon carcinoma cells utilizing MAbs D612 and GA733 revealed no cross-reactivity between these antibodies. Similarly, competitive binding studies between MAbs 17-1A and KS1/4 and MAb D612 revealed no similarity between the epitopes recognized by MAb D612 and MAbs 17-1A and KS1/4. MAbs D612 and 17-1A were also titered in immunoperoxidase staining assays on serial frozen sections of normal and malignant colon. MAb D612 showed a higher titer of immunostaining reactivity with both normal and malignant colon than did MAb 17-1A. MAb D612 showed roughly equivalent immunostaining titers against normal and malignant colon; whereas MAb 17-1A showed higher titer of immunostaining reactivity against the normal colon tissue than against the malignant colon. Flow cytometric analysis of phosphatidylinositol-specific phospholipase C-treated colon carcinoma cells revealed no loss of D612 antigen from the cell surface, suggesting that the mechanisms of attachment of the D612 antigen to the cell surface does not involve linkage to a phosphatidylinositol glycan.(ABSTRACT TRUNCATED AT 400 WORDS)

Serological mapping of the TAG-72 tumor-associated antigen using 19 distinct monoclonal antibodies.

Monoclonal antibody (MAb) B72.3 has been shown to be of potential utility in the management of human carcinoma via its use in (a) the targeting of carcinoma lesions in colorectal and ovarian cancer patients, (b) immunohistochemical analyses of biopsies and effusions, and (c) serum assays to help define the presence of carcinoma. The B72.3-reactive antigen, designated tumor-associated glycoprotein 72 (TAG-72), has been characterized as a high molecular weight glycoprotein with the properties of a mucin. We report here the utilization of MAb B72.3 and 18 second generation MAbs (generated using purified TAG-72 obtained from a colon carcinoma xenograft as immunogen) to construct a serological map of the TAG-72 molecule. The generation and initial characterization of 10 of the second generation MAbs have been described previously; in addition, eight previously unreported MAbs were used. All 19 MAbs produced immune precipitate lines against purified TAG-72 in double immunodiffusion, indicating that each epitope recognized by a single MAb is present at least twice on the TAG-72 molecule. Immunodepletion analyses utilizing 11 of the anti-TAG-72 MAbs indicated that each recognizes the same molecule or population of molecules. Nineteen competition radioimmunoassays were developed and 19 purified competitor immunoglobulins were used in each assay. The patterns of cross-competition indicated the presence of a complex array of tumor-associated epitopes on the TAG-72 molecule. Some of the MAbs recognized epitopes that were structurally or spatially related to one another, but none appeared to recognize identical epitopes. The spectrum of inhibitory reactivities of these MAbs for TAG-72 binding varied from extremely restricted to more broad inhibition. The serological mapping studies reported here provide information as to the range and nature of the epitopes expressed on the TAG-72 molecule, help form the basis for selecting alternative anti-TAG-72 MAbs for use in potential clinical applications, and further define the nature of this oncofetal antigen.

Transduction and expression of the human carcinoembryonic antigen gene in a murine colon carcinoma cell line.

A cell line derived from the mouse colon adenocarcinoma, MC-38, has been transduced with a retroviral construct containing complementary DNA encoding the human carcinoembryonic antigen (CEA) gene. MC-38, which forms tumors in syngeneic C57BL/6 mice, has been extensively studied as a target for active immunotherapy. Individual transduced clones that express high levels of cell surface CEA were isolated, and two clones, termed MC-38-ceal and MC-38-cea2, were extensively characterized. The levels of CEA found on the surface of these clones were considerably higher than that found in a moderately differentiated human colon carcinoma cell line (WiDr) and were comparable to those found on the human colon carcinoma cell lines GEO and CBS (among the highest CEA-expressing cells reported). Further analysis demonstrated that the CEA expressed in the MC-38-cea1 clone had a similar molecular weight to native CEA (Mr 180,000), but the MC-38-cea2 cell line expressed a single Mr 70,000 glycosylated immunoreactive product. Seven anti-CEA monoclonal antibodies were found to react with both clones. The CEA gene present in the MC-38-cea2 clone was partially sequenced and was found to contain a deletion of two of the three repeated domains present in CEA. These results provide a basis for future studies to map immunodominant epitopes of CEA and to develop a syngeneic model system that may aid in the design of reagents and protocols to study active and passive immunotherapy directed against a carcinoma expressing human CEA.

Upper aerodigestive neoplasm perpetuated in the nude mouse.

The ability to study and characterize squamous cell cancer of the upper aerodigestive system would be greatly facilitated by an in vivo model. The subsequent opportunity to observe cellular kinetics, membrane antigenicity and hence, potential response to chemotherapy, immunotherapy, radiotherapy, or a combination of these treatment modalities would most likely have early and significant clinical relevance. A multidisciplinary team of basic scientists and clinicians have developed a nude mouse colony for such investigational research. Melanoma and pulmonary squamous and pulmonary adenocarcinoma have been grown and successfully transferred. In addition, head and neck squamous cell carcinoma from multiple sites have also been successfully colonized. We present our experience with this interesting in vivo model and discuss problems in creating a nude mouse colony, techniques of successful tumor inoculation, ongoing maintenance of successful cell lines, and theoretical advantages for potential clinical investigations using this dynamic biologic system.

Dose-ranging study of a single injection of pneumococcal conjugate vaccine (1 ×, 2 ×, or 4 ×) in healthy subjects aged 70 years or older.

Healthy adults aged ≥ 70 years (N=443) with no history of pneumococcal vaccination received 7- or 9-valent pneumococcal conjugate vaccine (PCV7 or PCV9) at 1 × (PCV7 only), 2 × (PCV7+PCV9), or 4 × (2 × PCV7+2 × PCV9) dosage in a randomised, open-label study evaluating pneumococcal protein conjugate vaccine (PnC). Controls received 23-valent pneumococcal polysaccharide vaccine (PPV). Both geometric mean concentration enzyme-linked immunosorbent assay and opsonophagocytic activity antibody titres assessed 1 month after vaccination were significantly increased over baseline titres for all PCV7 serotypes, with a trend toward a dose-dependent immune response. Local reactions for the 4 × dose, but not the 2 × dose, were statistically significantly higher than for the 1 × dose. No treatment-related serious adverse events occurred.

Establishment of a new human pneumococcal standard reference serum, 007sp.

Lot 89SF has been the reference standard serum pool used in pneumococcal enzyme-linked immunosorbent assays (ELISAs) since 1990. In 2005, it was estimated that there remained between 2 and 5 years' supply of lot 89SF. Since lot 89SF was the reference standard used in the evaluation of the seven-valent pneumococcal conjugate vaccine Prevnar (PCV7), the link to clinical efficacy would be severed if stocks became completely depleted. Furthermore, demonstration of immune responses comparable to those elicited by PCV7 is a licensure approach used for new pneumococcal conjugate vaccines, so a replacement reference standard was required. A total of 278 volunteers were immunized with the 23-valent unconjugated polysaccharide vaccine Pneumovax II, and a unit of blood was obtained twice within 120 days following immunization. Plasma was prepared, pooled, and confirmed to be free from hepatitis B virus (HBV), hepatitis C virus (HCV), and HIV. The pooled serum was poured at 6 ml per vial into 15,333 vials and lyophilized. Immunological bridging of 007sp to 89SF was used to establish equivalent reference values for 13 pneumococcal capsular serotypes (1, 3, 4, 5, 6A, 6B, 7F, 9V, 14, 18C, 19A, 19F and 23F) by five independent laboratories. Antibody concentrations in 007sp were established relative to the lot 89SF reference preparation using the WHO reference ELISA. Subsequently, 12 existing WHO calibration sera had concentrations reassigned for 13 pneumococcal serotypes using new serum 007sp as the reference, and these were compared to concentrations relative to the original reference serum. Agreement was excellent for the 12 WHO calibration sera. The 007sp preparation has replaced 89SF as the pneumococcal reference standard. Sufficient quantity of this new preparation is available such that, with judicious use, it should be available for at least 25 years.

Cell-type specificity of anti-CD45 autoantibodies in systemic lupus erythematosus.

OBJECTIVE: To determine the specificity of anti-CD45 autoantibodies in systemic lupus erythematosus (SLE) for native CD45 and for CD45 expressed by T cells and B cells, and at different stages of cellular activation. METHODS: CD45 purified from different types of lymphocytes was examined by immunoblotting with sera from patients with SLE. Indirect immunofluorescence experiments were performed with purified anti-CD45 autoantibodies. RESULTS: IgM anti-CD45 autoantibodies in SLE recognize native CD45 expressed on the surface membrane of viable lymphocytes and CD45 purified from activated peripheral T cells and certain T cell lines, but not CD45 purified from B cells or resting peripheral T cells. The presence or absence of reactivity is independent of the individual isoforms expressed. CONCLUSION: Recognition of CD45 by IgM antilymphocyte autoantibodies in SLE varies with the lineage and state of activation of the lymphocyte target. This pattern of reactivity is consistent with autoantibody specificities involving CD45 glycoforms, rather than CD45 isoforms.

Autoantibodies to CD45 in systemic lupus erythematosus.

Autoantibodies to surface antigens on lymphocytes and other cells of the immune system may contribute to the development of immunoregulatory and other cellular immune abnormalities in patients with active systemic lupus erythematosus. Of special interest in this respect are autoantibodies to CD45 (leukocyte-common antigen, T200), a plasma membrane protein tyrosine phosphatase implicated in the regulation of lymphocyte functional activity, including cytotoxicity, proliferation, and differentiation.

Antigenic mimicry of a human cellular polypeptide by Mycoplasma hyorhinis.

A 46-kilodalton (kDa) polypeptide was immunoprecipitated from radiolabeled extracts of human cell lines infected with Mycoplasma hyorhinis by murine monoclonal antibodies PF/2A and ML77. Both of these antibodies also reacted in an enzyme-linked immunosorbent assay (ELISA) with M. hyorhinis cells and with human and nonhuman cell lines infected with M. hyorhinis but failed to react with A7573 cells infected with any of 10 other species of the order Mycoplasmatales. PF/2A also reacted in the ELISA with certain human cell lines that were demonstrated to be free of mycoplasma infection. From extracts of these lines, a polypeptide antigen that appeared as a 24-kDa doublet on polyacrylamide gels was immunoprecipitated by PF/2A. When the PF/2A-reactive human cell lines were infected by M. hyorhinis, both the 46- and 24-kDa antigens were immunoprecipitated by PF/2A. ML77 did not react in the ELISA with any noninfected human cells tested and failed to immunoprecipitate a 24-kDa component from any human cells. In Western blotting analyses of extracts of M. hyorhinis cells, both PF/2A and ML77 stained a 46-kDa band. PF/2A also stained 24-kDa bands in Western blotting analyses of reactive human cells and M. hyorhinis cells, although a 24-kDa component was not precipitated from extracts of M. hyorhinis cells by PF/2A.

Expression of the sialosyl-Tn epitope on CD45 derived from activated peripheral blood T cells.

The cell surface protein tyrosine phosphatase CD45 is a major target of IgM anti-T cell autoantibodies in systemic lupus erythematosus (SLE). The autoreactive determinants on CD45 are O-linked glycans expressed on activated T cells and certain T cell lines, rather than linear or conformational polypeptide epitopes or N-linked glycans. To identify oligosaccharide structures that may play a role in the functional interactions of CD45 or are candidate target epitopes of SLE anti-CD45 autoantibodies, autoreactive CD45 purified from Jurkat T cells and non-autoreactive CD45 purified from CLL B cells were tested by ELISA for expression of mucin-type O-glycan structures. Monoclonal antibodies (mAbs) directed against blood group A, type 1 H chains, type 2 H chains, T, Le(a), sialylated-Le(a), Le(b), sialylated-Le(c), Le(x), sialylated-Le(x), multi-fucosylated Le(x), Le(y), and sialylated-extended Le(v) failed to react with CD45 from either B cells or T cells. However, mAbs directed against Tn (galNAcalpha1-->O-ser/thr) or sialosyl-Tn (neuNAcalpha2-6gaINAcalpha1-->O-ser/thr) structures reacted with CD45 derived from Jurkat T cells, but not from CLL B cells. Anti-Tn mAbs also reacted in western blotting procedures with CD45 isolated from Jurkat T cells, but did not react with CD45 isolated from CEM, MOLT-3, or PEER T cells; Daudi, Raji, or CLL B cells; or resting or Con A-activated PBL. However, anti-sialosyl-Tn mAbs stained blots of CD45 isolated from Jurkat and CEM T cells and Con A-activated PBL, a pattern of reactivity similar to that of the anti-CD45 autoantibodies. Flow cytometric analyses demonstrated that the sialosyl-Tn epitopes are expressed on a subpopulation of CD4 +/CD8- T cells.

Carbohydrate specificity of IgM autoantibodies to CD45 in systemic lupus erythematosus.

Patients with SLE develop IgM autoantibodies to different isoforms of CD45, the major surface membrane protein tyrosine phosphatase on lymphocytes and other nucleated hemopoietic cells. Because such autoantibodies could have a potential role in the development of immune dysfunction in this disorder, we performed a series of experiments to characterize their antigenic specificity further. Blots of recombinant E. coli fusion proteins encoded by exons 3-7 of the p220 and p180 isoforms were uniformly non-reactive with SLE IgM, suggesting that anti-CD45 autoantibodies in SLE are directed against conformational and/or carbohydrate epitopes, rather than linear polypeptide epitopes. This issue was examined further using chemically and enzymatically modified CD45 purified from T cells by lectin affinity chromatography as substrates. Treatment of CD45 with 25 mM sodium-m-periodate, sufficient to abrogate binding to various lectins, abolished the reactivity with SLE anti-CD45 autoantibodies. On the other hand, digestion of CD45 with neuraminidase enhanced the binding of anti-CD45 autoantibodies from some of the SLE sera. This result probably reflects decreased steric hindrance or charge repulsion because the binding of mouse monoclonal antibodies directed against linear polypeptide epitopes of CD45 was similarly enhanced. Digestion of CD45 with N-glycosidase F had no effect on autoantibody staining. Taken together, these data suggest that IgM anti-CD45 autoantibodies in SLE recognize non-sialylated carbohydrate determinants in the highly O-glycosylated polymorphic domains of CD45.

Glycoprotein specificity of cold-reactive IgM antilymphocyte autoantibodies in systemic lupus erythematosus.

Sera from patients with systemic lupus erythematosus frequently contain IgM antibodies to glycoproteins of Mr 46,000 and approximately 200,000 isolated from nonionic detergent lysates of mature T cells by affinity chromatography with solid-phase wheat germ agglutinin. Autoantibodies of this specificity correlate strongly with the presence of IgM anti-T cell autoantibodies, as determined by independent indirect immunofluorescence and complement-dependent microcytotoxicity assays, and are specifically absorbed by incubation of patient serum with viable T cells. Collectively, the data suggest that gp46 and, to a lesser extent, gp approximately 200 represent major targets of IgM antilymphocyte autoantibodies in systemic lupus erythematosus.